drm: amdgpu: pm: Mark vangogh_clk_dpm_is_enabled() as static

kernel test robot throws below warnings ->

drivers/gpu/drm/amd/amdgpu/../pm/swsmu/smu11/vangogh_ppt.c:594:6:
warning: no previous prototype for 'vangogh_clk_dpm_is_enabled'
[-Wmissing-prototypes]
drivers/gpu/drm/amd/amdgpu/../pm/swsmu/smu11/vangogh_ppt.c:594:6:
warning: no previous prototype for function 'vangogh_clk_dpm_is_enabled'
[-Wmissing-prototypes]

Mark vangogh_clk_dpm_is_enabled() as static.
Reviewed-by: Huang Rui <ray.huang@amd.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/swsmu/smu11/vangogh_ppt.c

@@ -585,7 +585,7 @@ static int vangogh_get_profiling_clk_mask(struct smu_context *smu,
 	return 0;
 }
 
-bool vangogh_clk_dpm_is_enabled(struct smu_context *smu,
+static bool vangogh_clk_dpm_is_enabled(struct smu_context *smu,
 				enum smu_clk_type clk_type)
 {
 	enum smu_feature_mask feature_id = 0;